(1) Field of the Invention
This invention relates to a method for controlling a projecting system, and more particularly relates to a method for controlling a cooling device of a projecting system.
(2) Description of the Prior Art
The development of projecting technology in present has a tendency toward the objects of small size, high brightness, and low noise. In order to achieve the object of high brightness, a high intensity light source must be used to show a clear and bright image. The light source applied in most projecting systems nowadays is the high intensity discharge (HID) lamp, such as the metal halide lamp (MHL), the ultra high pressure (UHP) mercury lamp, the xenon arc lamp, and etc.
The lamp of the projecting system usually operates under high operating temperature. Take the UHP mercury lamp for example. As the lamp is operating, the pressure will be enhanced to about 200 Pa and the operating temperature to about 1000° C. Due to the high operating temperature, the cooling device such as a fan is critical for normal operation of projecting system. That is, the cooling device must be started to remove the heat generated by the lamp as the projecting system is operating so as to keep the interior temperature of the projecting system below a predetermined temperature to maintain the normal operation of the projecting system.
The operation character of the lamp is mentioned below. Take the UHP mercury lamp for example. As the lamp is lighted, a plasma arc is generated between the opposite electrodes thereof, and the liquid mercury in the lamp is evaporated to generate strong illumination. Since mercury vapor is not a good conductor, the plasma arc for lighting the lamp can be generated only as the mercury in the lamp is in liquid state. That is, after reaching the operating temperature (about 1000° C.), the mercury lamp must be properly cooled below the boiling temperature of mercury (about 450° C.) or the mercury lamp cannot be re-lighted.
After the lamp is turned off, the projecting system in present usually has the cooling device keep operating for a predetermined period to cool the lamp. This procedure may prevent the lamp from exploding and guarantee lighted as the projecting system is restarted. However, the above mentioned method has the drawback that since the heat dissipation ability of cooling device is influenced by the operating environment of the projecting system, the temperature of the mercury within the lamp may be still too high to have the lamp lighted as located in a poor heat-dissipation environment, such as a closed space.
Accordingly, the present invention focuses on the above mention drawback about the traditional method for cooling projecting systems and provides a method to solve this problem. This method detects the lighting event of the projecting system so as to adjust the cooling period of the projecting system automatically. In addition, the method provided in the present invention may figure out a best cooling period for the projecting system according to the operating environment so as to reduce the failure rate of lighting, extend the life of lamp, and reduce the waiting time once the lighting fails.